The arithmetic sequence $(a_i)$ is defined by the formula: $a_i = -3 + 6(i - 1)$ What is $a_{19}$, the nineteenth term in the sequence?
Answer: From the given formula, we can see that the first term of the sequence is $-3$ and the common difference is $6$ To find $a_{19}$ , we can simply substitute $i = 19$ into the given formula. Therefore, the nineteenth term is equal to $a_{19} = -3 + 6 (19 - 1) = 105$.